Those who drive vehicles on ice frequently have trouble controlling the spin of the vehicle's drive wheels. Ice severely reduces the traction between the drive wheels and the road surface. As a result, even a small amount of torque applied to the drive wheels tends to cause them to spin. If the spin becomes severe, the vehicle can be difficult to control.
There have been attempts to control vehicular wheel spin in the past. The one such approach is shown in U.S. Pat. No. 5,022,483 filed in the name of Tsuyama et al. and issued Jun. 11, 1991 (hereafter the "'483 patent"). Such attempts have failed to provide the degree of control needed by ordinary drivers under icy road conditions. For example, as explained in column 11, lines 61-65 of the '483 patent, the spark angle is altered according to the slip value of a driven wheel. The greater the slip value, the greater the correction of the spark angle. The applicants have found that such elementary spark angle control is insufficient to provide a degree of wheel spin control that will satisfy the needs of ordinary drivers. For example, relying on slip value alone creates problems during typical operating conditions.
Accordingly, it is the primary object of the present invention to provide improved techniques for controlling the spin of driven wheels of a vehicle that also includes non-driven wheels and an engine controlled by spark angle.
Another object of the invention is to provide such techniques for vehicles that also include an engine controlled by throttle position.